get rid of the B&M sleeve for the TV .
these can cause poor shift patterns changes. They do not provide detent oil for a forced kick down out of over drive.
The TV bore where the Transgo Valve is could be worn enough that oil is bypassing and causing problems too.
Install the OE TV plunger sleeve and see what hapens.
I am curious what weights are in the governor.
Real light weights can cause late shifts . Some situations the engine will float valves before the tranny shifts if the governor weights and shift valve springs in the valve body are mis matched bad enough.
Dont worry how old you are... it is the mileage on your body that adds up.